1. Field of the Invention
The present invention relates to a processing apparatus that utilizes the nanoimprint technology.
2. Description of the Related Art
A conventional projection exposure apparatus manufactures a fine structure using the lithography, such as an electronic circuit, a Micro Electro-Mechanical System (“MEMS”), and a grating lens. The projection exposure apparatus transfers and projects a reduced pattern of a mask or reticle onto a substrate, such as silicon and glass, to which a resist or photosensitive agent is applied. The projection optical system can form a very fine structure, but is too expensive to be readily available.
Accordingly, the nanoimprint calls attentions as a low cost patterning method that can form a very fine structure. The nanoimprint transfers a fine pattern to a resist by pressing a model or mold having the pattern, which is formed by an electron beam exposure, etc., against a wafer to which a resinous material or the resist is applied. The nanoimprint needs only a mold and a pressure mechanism that compresses the mold against the resinous material, and can provide fine processing inexpensively. The current nanoimprint can transfer a fine shape of about 10 nm, and have sufficiently fine processing performance. The nanoimprint is expected to apply to new devices, in particular, a fine periodic structure forming means of a magnetic recording medium, which have not been manufactured because they are unprofitable to the projection exposure apparatus.
Some transfer methods are proposed for the nanoimprint, such as a heat cycle method and a photo-curing (or UV curing) method. The heat cycle method is a method that heats a resin to be processed (or a thermoplastic material) up to a glass transition temperature or above (or enhances the resin's flowability), and pressures, cools, and then releases the mold. The photo-curing method is a method that exposes and cures the UV curing resin, while pressing the resin with a transparent mold.
The photo-curing method can comparatively easily control the temperature, and thus is suitable for the manufacture of a semiconductor device. The manufacture of the semiconductor device needs highly precise overlay accuracy, which is the accuracy necessary to overlap several patterns on the substrate. The photo-curing method allows an alignment mark on a substrate to be observed through a transparent mold, and is suitable for the manufacture of the semiconductor device from a viewpoint of the alignment. On the other hand, the heat cycle method includes the heating step, thermally expands due to the temperature rises of the substrate and the mold, and has difficulties in maintaining the overlay accuracy.
FIGS. 13A-13C are views for explaining the nanoimprint that adopts the photo-curing method. FIG. 13A shows the pressing step. FIG. 13B shows the curing step. FIG. 13C shows the releasing step. A mold MP is made of a UV transmitting material, such as quartz, is pressed against a substrate (wafer) ST to which a UV curing resin UCR is applied. The UV curing resin UCR moves along a pattern formed on the mold MP.
Ultraviolet UL is irradiated as shown in FIG. 13B while the mold MP is pressed against the substrate ST, thereby curing the UV curing resin UCR in a shape (pattern) of the mold MP. Then, the mold MP is parted, as shown in FIG. 13C, from the substrate ST. As a result, the UV curing resin UCR that maintains the shape of the mold MP remains on the substrate ST, and the pattern is transferred to the substrate ST. For a large substrate, a substrate is stepped for each pattern transfer, and the above step is repeated to sequentially transfer the pattern to the entire substrate. The transferred resin or resist pattern is equivalent to the resist pattern transferred by the projection exposure apparatus once the pattern's primary coat is removed.
In a production site used to produce a large amount of articles, which is not limited to the manufacture of a semiconductor device, the productivity of a manufacturing apparatus is also required. Even when the manufacturing apparatus is less expensive, the total production cost does not become low if the production capability is low.
Currently, a universal exposure apparatus, such as a stepper and a scanner, has a throughput of about 150 or which is the number of wafers that can be processed per unit time. The number of transfers per wafer is about 50 times (shots), and the exposure apparatus needs 1 second or below for each transfer. The nanoimprint transfer includes three steps, i.e., the pressing step, the curing step, and the releasing step. In order for the nanoimprint to realize the throughput equivalent to that of the exposure apparatus, these three steps should be completed within about one second.
Among these three steps, the curing step can be quickly completed by irradiating the UV having a high illuminance. For the pressing step, the ultrasonic vibration of the mold is proposed during pressing to lower the viscosity of the resin (resist), and to enhance the flowability, quickening the pressing step. For the releasing step, even when a mechanical action is quickened, a friction between the mold and the cured resist damages a pattern. Accordingly, one proposal performs a release facilitation process for the mold to improve its releasability. See U.S. Pat. No. 6,309,580 B1. Another proposal improves the releasability by obliquely forcing the mold or in a direction oblique to the mold's patterned plane during the release time. See U.S. Pat. No. 6,870,301 B1.
Nevertheless, the prior art cannot sufficiently satisfy the throughput required for the nanoimprint. For example, even when the release facilitation process is performed for the mold, it takes several seconds for the mold to release. The method that obliquely forces the mold during releasing can lessen damages of the pattern formed on the resist, but does not necessarily quicken the releasing step or provide the fast releasing step.
The releasing step moves the mold at a low speed, as discussed later, so that the pattern formed on the resist does not get damaged when the mold parts from the resist. In other words, the releasing step continues to move the mold at a speed at which the mold is parted from the resist or a speed that does not damage the pattern formed on the resist. The releasing step maintains constant not only the mold speed but also a load between the mold and the resist. The releasing step does not damage the pattern formed on the resist, but needs a long time.